fn main() {
    let x = 5;

    let y = {
        let x = 3;
        x + 1
    };

    println!("x 的值为 : {}", x);
    println!("y 的值为 : {}", y);

    fn five() -> i32 {
        5
    }
    println!("five() 的值为: {}", five());
}